(define (fringe items)
    (if (null? items)
        `()
        (append 
            (if (list? (car items))
                (fringe (car items))
                (list (car items))
            )
            (fringe (cdr items))
        )
    )
)



(define x (list (list 1 2) (list 3 4)))
(display x)
(newline)
(display (fringe x))
(newline)
(display (fringe (list x x)))
(exit)